1. Field of the Invention
The present invention relates to the field of battery protection, and in particular, to a battery protection circuit and system.
2. Description of Related Art
Portable electronic devices, such as digital cameras, cell phones, tablet computers, portable audio/visual devices or Bluetooth devices, employ increasingly lithium batteries as a major power. The lithium battery has many advantages including small size, high energy density, no memory effect, long cycle life, high battery voltage and low self-discharge rate. Due to these characteristics, the lithium battery is likely to explode or to be damaged, thus, attention must be paid to the safety when charging and discharging.
A protection chip is specially designed to protect the battery. The battery protected by a protection chip supplies power to the electronic device. FIG. 1 is a circuit diagram showing a conventional battery protection circuit for an electronic device. The battery protection circuit of FIG. 1 includes a battery BT1, a battery protection chip VM, a power switch MN1, a power switch MN2, a resistor R1, a resistor R2, a capacitor C1 and a protection control circuit P1. The protection control circuit P1 includes a charging circuit, a power management circuit, a power detection circuit T1, a resistor R3 and a resistor R4. When a voltage of the battery BT1 is higher than a charging voltage protection threshold, an output CO of the battery protection chip becomes a low level and the power switch NM2 switches off, thereby cutting off a charging path of the battery BT1 to prohibit further charging. When the voltage of the battery is lower than a discharging voltage protection threshold, an output DO of the battery protection chip turns to the low level, the power switch NM1 is switched off, thereby cutting off a discharging path of the battery BT1 to prohibit further discharging.
The battery protection circuit is necessary for lithium battery. However, a discharging current needs to flow through the power switches MN1 and MN2, thereby increasing power consumption of the battery protection circuit and lowering power supply efficiency.
Therefore, an improved technical solution is necessarily to be provided to overcome the above and other problems.